Transcatheter aortic valve replacement and stroke: a comprehensive review

2. Stroke incidence following TAVR (Figure 1)

In an effort to adjust for discrepancies in the definitions of stroke used in various studies, the Valve Academic Research Consortium has provided definitions of transient ischemic attack (TIA) and stroke.[10],[11] TIA is defined as a new neurological deficit that resolves rapidly, in less than 24 h (usually within 1–2 h), without evidence of tissue injury in neuroimaging. Stroke is defined as new focal or global neurological deficit that persists for more than 24 h and is thought to be embolic, ischemic or hemorrhagic.[11] The severity of stroke is usually categorized according to the modified Rankin Scale (mRS).

As will be discussed, the procedure of TAVR carries an inherent risk of stroke, which however continues to accrue with extended follow-up. Therefore, we should evaluate stroke risk with TAVR relative to the stroke risk of a similar patient population treated either medically, or with conventional SAVR, during the same follow-up period. Data from PARTNER 1B, study showed that medically treated patients had a 30-days stroke/TIA risk of 1.7%, and a 1-year risk of 4.5%, compared with corresponding risks of 6.7% and 10.6% in high risk TAVR patients.[4] Early experience with TAVR was associated with stroke rates nearly twice as high compared to SAVR.[12],[13] Data from the PARTNER 1A study showed a risk of neurologic events with SAVR of 2.4% at 30 days and 4.3% at one year, with corresponding rates for TAVR of 5.5% and 8.3%, respectively.[12] Generally, in high risk patients, the risk of stroke following SAVR is approximately 2%–4%.[14] Hence, it is reasonable to speculate that violent manipulation of a calcified aorta and stenotic aortic valve with TAVR results in a higher frequency of cerebral events, through debris embolization, compared to SAVR during which debris removal and cross-clamping of the aorta is involved.[15] On the contrary, the long-term risk of stroke following TAVR is somewhat similar to that of medically and/or surgically treated patients, and depends on their profile.[15] In a much larger analysis of PARTNER trial including the continued access registry with 2621 patients, the 30-days, 1-year and 3-year stroke rate were 3.3% (85% of them within one week), 5.4% and 6.9%, respectively.[11]

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In the randomized controlled trial of the self-expandable valve bioprosthesis (CoreValve, Medtronic, Minneapolis, MN) vs. SAVR in relatively high surgical risk patients (STS score 7.4%), the rates of stroke at 30 days and 1 year did not differ significantly between the two groups (4.9% vs. 6.2%, P = 0.46, and 8.8% vs. 12.6%, P = 0.1, respectively).[7] A recent report including 3687 patients from the CoreValve US Extreme Risk and High Risk Pivotal Trials or Continued Access Study, the 1-year stroke rate after TAVR was 8.4%, with a frequency of major stroke 2.8% at 30 days, and 5% at 1 year.[16] The frequency of TIA within 30 days was 0.5%, and within the first year 2.1%. Following initial experience with TAVR, various studies reported a range of stroke of 0–3.9% vs. 0.5%–5.7% with SAVR.[7],[17],[18] Similarly, according to published registries, the overall incidence rate of stroke in high-risk patients after TAVR varied from 1.7% to 4.8%.[17],[19][22] An earlier meta-analysis including 10,037 patients subjected to TAVR in various studies published between 2004/01 and 2011/11 reported a total 30-days stroke rate of 3.3% ± 1.8% (nearly all major strokes), which increased at 1-year to 5.2% ± 3.4%.[15] Two recent meta-analyses, one including seven European TAVR registries (9786 patients),[23] and another including 29,034 patients,[9] treated with both SAPIEN and CoreValve bioprostheses and involving both transfemoral (TF) and transapical (TA) approaches, reported a 1-year incidence of stroke of approximately 3%.[23] Additionally, a recent report from 299 US hospitals (12,182 patients), reported a stroke rate of 4.1% at 1 year following TAVR.[24] Finally, in a review of studies comparing TAVI vs. SAVR in patients with severe aortic stenosis and a mean risk score of 8% or less, the hazard for stroke was lower with TAVI (20 fewer per 1000 patients), however with a broad confidence interval (HR: 0.81, 95% CI: 0.63–1.01).[25] Additionally, an analysis of patients with an STS PROM risk score < 7 revealed lower albeit not statistically significant stroke rates after TAVR compared with SAVR at 30 days (4.9% vs. 6.3%, P = 0.46).[26]

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Thus, following the initial observation of a higher stroke rate with TAVR when compared to SAVR, latest studies, registries, and meta-analysis repetitively and constantly confirm that the incidence of stroke after TAVR decreased to rates comparable with those with SAVR.[7],[15],[19],[23][28] This may be due to inclusion of lower risk patients compared to initial study cohorts, and to evolution of valve technology and implantation technique.

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About the Author: Tung Chi